Resistor material



Patented Aug. 16, 1927.

UNITED. STATES PAT N 4 OFFICE.

OSEPH SLEPIAN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

' masrsron. Kareem.

Io Drawing. Application filed Kay 7,

This invention relates'to resistors -or re- It has beenco minon practice to make nona metallic resistors of ceramic materials including a kaolin binder, conducting materials, such as raplhte or carboi'fi'fidum,

and filler materias, such as slhca, to provide the proper resistance, and to bake the same mat a high temperature.

It has been found that, because of variatio in the sizes of granules, imperfect control of firing condltions and of tempera-.

tures and time periods of baking, it was 1 ditiicult to control the resistance in resistors,

made from the same batch of such materials with any degree of certainty. The specific resistance thereof varied greatly and, in Toremvwarr. I provide a saturat service, changed as much as several hundred 2 percent in a relatively short time.

It has also been proposed to substitute for I the kaolin binder a binder such aswater lass and, instead of baking, simply drymg the resistor material to remove water. .But the resistance of such material has been found advantages of the materials of the prior art,

which shall be stable and permanent and the manufacture of which may be controlled very closely.

In practising my invention, I provide a non-crystalline binder such as a silicate. an alkali me a an able mixture of ductin materials. The fo'rmed reslstbrs are 5 E a luminate stannate or the like of t l d lncorporate the same m a 5m conductin and non-cona e to remove water and are then treated with a substance which is capable-of reduc ing the sensitiveness thereof to humidity by removing at e st .p er ...afmthe.a aal from comb'iiiatio n with tlie-binderaiiil which preferabl combines with the alkali to provlde a solub e combination. The material is then washed to remove the alkali therefrom and 'tlie i esistor is dr ied or baked A specific example'df Tny invention is as -l bi followsz I make a dry mixture of 4.5

ohms per centimeter cube.

1923. Serial No. 637,147.

1am black and 95.5% flint which calcu sistor materials, more particularlytoresistor lated to provide afinal resistivity of material of a non-metallic nature.

A mixture of. this kind may be stored for. relatively long periods of time without changes or deterioration therein. A solution of sodium silicate or commercial water "lass ls-dlluted to the desired strength and a sultable amountthereof mixed with the resistor material to give a consistency suitable for molding. The amount of water glass is relatively small. baked at a sufficiently higli tei'fe'rature to w remove most of the water there rom.

If desired, the resistors may be strengthened by impregna tingthe sa-me a water glass solution and again baking ofdfing ecl solution of a material capable of removing the alkali from the combination thereof with Resistors are molded and then the silica, such as ammonium chloride, and

immerse the resistors tEereln for a suitable length of time at room temperature, in a vacuum, if desired. The time of treatment is from one to two hours. The resistors are then removed from the solution and a stream of water passed over the-same slowly for a period of from four to five hours to wash out the soluble alkali chloride formed in the treatment. The resistors are then dried at a suitable temperature to remove water and free ammonia from the material.

Resistors made in accordance with my invention are remarkably constant in their resistivity, there being less than 20% variation in resistivity of resistors made from thesame mix compared toa variation for baked rcelain material of the same character of at least 500%. My resistors do not change in resistance either in t eatmosphere or under the influence of a ischarge such as the same may be subjected to when used in a lightning arrester. The steps of manufacture are very simple and various batches of materials may be made to agree closely in resistivity of the final product. Although I have described my invention, setting forth a specific embodiment thereof, my invention is not necessarily limited to the detailsdescribed. The binder need not be water lass but other colloidal binders may be sulistituted therefor.

It is not essential that ammonium chloride be used to substituted therefor. However, I prefer to use this substance because it leaves the $1- kali in a soluble combination, and the ammonia resulting from the reaction may be readil removed. If desired, the resistors may givenv several treatments with the alkali-removing agent and a corresponding number of washings and dryings. These and other changes may be made in my invention without dc arting from the principles herein set forth.

I claim as my invention:

' 1. The method of treating a solid resistor comprism conducting ingredients, insulating ingre ients and a hardened binder including a hygroscopic sodium silicate, which comprises su jecting the solid resistor to the action of ammonium chloride.

2."The methodof treating a solid resistor comprisin conducting ingredients insulatmg mgre 'ents and a hardened bmder including a hygroscopic sodium silicate, which comprises su jecting the solid resistor to the action of ammonium chloride, and subsequently washing .and drying the resistor to remove soluble alkaline substances contained therein.

3. The method of making solid composite resistors which comprises mlxing conducting ingredients, insulating in edients and water glass solution, forming e mixture into a resistor, hardening the resistor by evaporatin the water contained in the water glass SOfillE-lOIl and subjectin .said resistor to the action of ammomum c oride.

4. The method of making solid composite resistors which com rises mixing conducting ingredients, insulating ingredients and water glass solution, forming the inixture into a resistor, har

tion of ammonium chloride, and. subsedening the-resistor by evaporating the water contained in the water glass. so u subscribed tion, subjecting said reslstor to the ac-v remove therefrom soluble substances resultfrom the action of said ammonium chlo- 5. The method of treating1 molded hygroscopic articles utilizin a so uble alkah silicate as a binder, in or er to render said articles non-sensitive to humidity conditions in the atmosphere, which comprises treating said articles with a soluble salt such that the acid radical of the salt will form a soluble salt with the alkali insaid silicate and the base radical of the salt will form a compound which is readily removable from the composition, and subsequently washing and heatin said resistors.

7. e method of making a molded resistor body. which comprises mixing finely divided insulatin and conducting mgredients, adding a so ution containing an alkali silicate, moldin the resulting plastic mass and hardenin t e same, treating the article so formed wit a solution of a salt havingha volatile, readily'removable base, whereby t e alkali in said silicate is dissolved, and subsequently washm and heating said article by washing, and subsequently washing and y to remove both t e dissolved salt of the1alkali and the volatile base residue from the molded body.

' osEPH SLEPIAhLf testimony whereof, I have hereunto I my name this 2nd day of May, 

